A cordless telephone set has high convenience since a user can make a call to the other party through a cordless handset while being at a distance from a base unit connected to a telephone line. However, during a power failure, the base unit cannot obtain electric power from a power line and cannot communicate with the cordless handset. Thus, the user cannot make a call to the other party.
In this respect, a cordless telephone set has been proposed with which a user can make a call to the other party even during a power failure. For example, Patent Literature 1 discloses a cordless telephone set in which if it is detected that a radio link between a cordless handset and a base unit is cut off, a switch circuit of the cordless handset is switched, and thus, electric current from a battery flows in the base unit as backup current so that the base unit and the cordless handset can communicate with each other even during a power failure.